Head assembly for a cryogenic cooler

ABSTRACT

A head assembly having a molded plastic frusto-conical body is mated with a metal connector stem to supply a cryogenic cooling apparatus with a fluid under pressure for cooling a chamber by expansion through the Joule-Thomson effect. The molded plastic frusto-conical body has a spiral groove which extends from a base to a vortex. A tube attached to the connector has a finned section which is located in the spiral groove and a distribution section which is located adjacent the vortex. The spiral groove will direct cooled fluid from the chamber around and over the finned section to precool the fluid flowing therethrough. The plastic frusto-conical body will inhibit the transfer of thermal energy between the connector stem and the finned section to assure that cooled fluid flowing from the chamber can reduce the temperature of the fluid flowing in the finned section before being expanded upon entering the chamber through an orifice in the distribution section.

United States Patent Sollami HEAD ASSEMBLY FOR A CRYOGENIC COOLER Primary ExaminerWilliam P. ODea Assistant Examiner-Ronald C. Capossel Attorney, Agent, or Firm-Leo H. McCormick, Jr.; William N. Antonis 5 7 ABSTRACT A head assembly having a molded plastic frustoconical body is mated with a metal connector stem to supply a cryogenic cooling apparatus with a fluid under pressure for cooling a chamber by expansion through the Joule-Thomson effect. The molded plastic frusto-conical body has a spiral groove which extends from a base to a vortex. A tube attached to the connector has a finned section which is located in the spiral groove and a distribution section which is located adjacent the vortex. The spiral groove will direct cooled fluid from the chamber around and over the finned section to precool the fluid flowing therethrough. The plastic frusto-conical body will inhibit the transfer of thermal energy between the connector stem and the finned section to assure that cooled fluid flowing from the chamber can reduce the temperature of the fluid flowing in the finned section before being expanded upon entering the chamber through an orifice in the distribution section.

3 Claims, 2 Drawing Figures U.S. Patent Dec. 16, 1975 filly:

FIG. I

FlG.2

I haust fluid into close contact with the tube to precool 1 HEAD ASSEMBLY FOR A CRYOGENIC COOLER BACKGROUND OF THE INVENTION In known cryogenic cooling apparatus having a heat 5 exchanger formed by a finned tube wound around a cylindrical mandrel, it is necessary to wrap a filament adjacent the periphery of the fins to divert cooled exthe supply of fluid flowing therein.

As shown in-U.S. Pat. No; 3,400,757, The filament is wrapped around the cylindrical mandrel and an elastomeric sleeve fitted over the finned tube. The elastomeric sleeve. being a good insulator will prevent the conduction of heat outside the elastomeric sleeve from reaching the finned tube. However, it is still possible under some conditions fora themial energy loss to occur through the cylindrical mandrel. In most applications where this type of cryogenic cooling apparatus is used, a fluid such as air, nitrogen, or mixtures thereof under pressure is transmitted through the finned tube and out an orifice into a chamber. The fluid will expand in the chamber to produce a low temperature approaching liquid air in approximately a minute or two. Unfortunately some thermal energy losses can reduce the operating effectiveness to a point where the time required to reach a selected low temperature is increased twofold.

SUMMARY OF THE INVENTION I have devised a head for a cryogenic cooler whereby the thermal energy loss between a connector stem and a finned distribution tube means is reduced to an insignificant level. The head has a frusto-conical body with a spiral groove located on the periphery between the base and the vortex for retaining the finned distribution tube. A blind bore extends from the base toward the vortex for holding a head on the connector stem in a fixed position in order that the finned distribution tube will be aligned within the spiral groove. The frustoconical body is constructed of a plastic having a low thermal conductivity to prevent heat from being transmitted from the connector stem to the finned distribution tube. The spiral groove will direct the exhaust fluid from the expansion chamber into contact with the finned distribution tube to precool the fluid flowing therethrough.

It is therefore the object of this invention to provide a cryogenic cooler with a head means whereby the transfer of thermal energy between a connector stem and a finned distribution tube is inhibited by a low thermal conductive plastic body which retains the finned distribution tube.

It is another object of this invention to provide a frusto-conical body with a spiral groove for holding a finned distribution tube through which a pressurized fluid flows into an expansion chamber and for directing fluid from the expansion chamber into contact with the finned tube to precool the pressurized fluid flowing therethrough.

It is a further object of this invention to provide a head assembly for a cryogenic cooler whereby the transfer of thermal energy between a connector stem and a distribution means is inhibited by a low thermal conductive plastic barrier which directs cooled fluid into the distribution means to precool fluid flowing in the distribution means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a cryogenic cooler having a frusto-conical head having a spiral groove for holding a finned distribution tube.

FIG. 2 is a prospective view of the head assembly of FIG. 1 showing the spiral of the finned distribution tube.

0 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The cryogenic cooling apparatus 10 shown in FIG. 1 has a head assembly 12 located in a stepped bore 14 of a body 16. The body 16 contains or is in contact with a component such as a thermistor which is to be cooled. The stepped bore 14 has a tapered surface 18 which intersects a blind axial bore 20. The blind axial bore 20 forms an expansion chamber 22 with the head assembly 12.

The head assembly 12 has a connector stem 24 with a passageway 26 connected by conduit 28 to a source of fluid under pressure in storage container 30. The stem 24 has a head section 32 which is located in axial bore 34 of a low thermal conductive plastic body 36. The plastic body 36 has a frusto-conical shape with a base 38 and vortex 40. The axial bore 34 extends from base 38 toward the vortex 40. The plastic body 36 has a rib 42 which extends from the interior of the axial bore 34 into an annular channel 44 on the head 32 of the connector stem 24.

The passageway 26 has an opening 46 through which end 48 of the distribution finned tube means 50 is attached to the connector stem 24. The base 38 has a slot 52 which is aligned with the opening 46 to start the finned section 56 of the tube means 50 in a spiral groove 54 of the frusto-conical body 36 (see FIG. 2). The end of the finned section 56 is attached to a distribution section 58 by a weld bead 60. The distribution section 58 transverses the diameter of the vortex 40 of the frustoconical body 36. The distribution section 58 has an orifice 62 located in axial alignment with the axial bore 34. The distribution section 58 has a closed end 64 which is inserted into a recess 66 in the frustoconical body 36. A bead of weld 68 positively secures the end 64 to the finned section 56.

A thread of filament 70 of Terylene is wound around the exterior of the finned section 56 of the tube means 50 to prevent direct communication between the expansion chamber 22 and the atmosphere.

A band 72 of resilient material, while not necessary in all installations, is located around the top of frustoconical body 36 to assure that the finned section 56 is separated from the atmosphere.

MODE OF OPERATION OF THE PREFERRED EMBODIMENT When it is desirous to rapidly cool a body 16, valve 74 is opened to allow a pressurized fluid to flow from container 30 into supply conduit 28. The fluid will flow through passageway 26 out opening 46 into tube means 50. The fluid will flow in the tube 55 through the finned section 56 to the distribution section 58 and out the orifice 62. The fluid under pressure upon entering the chamber 22 will expand and cool the chamber 22 by the Joule-Thomson effect. In expanding the temperature of the fluid in chamber 22 will approach that of liquid air. The fluid in chamber 22 will be transmitted to the atmosphere by following a spiral path around and across the finned section 56 of the tube which in turn is spiraled around the frusto-conical body 36. The peaks 76 in the frusto-conical body 36 will directthe fluid flowing in the spiral path toward the interior of the finned tube means 50 to cool the fluid flowing in tube 55. Upon reaching the end of the spiral groove, the cooled fluid will flow through slot 78 into the atmosphere. Since the frusto-conical body is of a low thermal conductive material, the cooled fluid flowing from the chamber 22 will rapidly cool tube 55 in the finned section 56 of the finned tube means 50 to precool the fluid flowing therein before it expands in the chamber 22. That is, the more effectively the tube 55 of the finned section can be cooled, the faster the fluid flowing into chamber 22 can cool body 16.

I claim:

1. A head assembly for a cryogenic cooling apparatus comprising:

a housing having a first blind bore therein, said first blind bore having a first section joined to a second section by a tapered section;

a frusto-conica] body having a base and a vortex with a second blind bore which extends from the base toward the vortex, said body having a spiral groove which extends from said base to the vortex, said frusto-conical body having an annular rib extending from said second blind bore, said frusto-conical body having a slot which extends from said second blind bore to said spiral groove, said frusto-conical body engaging said tapered section to create a chamber between the vortex and the second section of the first blind bore;

stem means having a head section and a connector section, said connector section having an axial passage which extends toward the head section, said axial passage having an opening adjacent the base of the frusto-conical body when said head section is secured in said axial bore, said connector section having an annular channel located in the head section for engaging said annular rib in the second blind bore for rigidly holding said stem means in a fixed position, said connector section transmitting a source of fluid under pressure to said opening; and

tube means located in said slot in said frusto-conical body and connected to said opening in the stem means having a finned section located in the spiral groove in the frusto-conical body and a distribution section located adjacent the vortex of the frustoconical body, said distribution section having a closed end and an orifice located along a line concurrent with the axial bore, said orifice permitting said fluid to expand in said chamber and cool by the Joule-Thomson efiect, said fluid in said chamber upon cooling being directed by said spiral groove through the finned section to precool the fluid flowing to the distribution section, said frustoconical body being a non-metal through which heat transfer is inhibited to prevent the stem means from being cooled by conduction of the cooled fluid present in said chamber and flowing in said spiral groove.

2. The head assembly, as recited in claim 1, wherein said frusto-conical head includes:

a recess located in said vortex adjacent the spiral groove to hold the orifice of the distribution section in axial alignment with said second blind bore.

3. The head assembly, as recited in claim 2, wherein said frusto-conical head section further includes;

fastener means attached to said distribution section and the finned section to prevent relative movement therebetween. 

1. A head assembly for a cryogenic cooling apparatus comprising: a housing having a first blind bore therein, said first blind bore having a first section joined to a second section by a tapered section; a frusto-conical body having a base and a vortex with a second blind bore which extends from the base toward the vortex, said body having a spiral groove which extends from said base to the vortex, said frusto-conical body having an annular rib extending from said second blind bore, said frusto-conical body having a slot which extends from said second blind bore to said spiral groove, said frusto-conical body engaging said tapered section to create a chamber between the vortex and the second section of the first blind bore; stem means having a head section and a connector section, said connector section having an axial passage which extends toward the head section, said axial passage having an opening adjacent the base of the frusto-conical body when said head section is secured in said axial bore, said connector section having an annular channel located in the head section for engaging said annular rib in the second blind bore for rigidly holding said stem means in a fixed position, said connector section transmitting a source of fluid under pressure to said opening; and tube means located in said slot in said frusto-conical body and connected to said opening in the stem means having a finned section located in the spiral groove in the frusto-conical body and a distribution section located adjacent the vortex of the frusto-conical body, said distribution section having a closed end and an orifice located along a line concurrent with the axial bore, said orifice permitting said fluid to expand in said chamber and cool by the Joule-Thomson effect, said fluid in said chamber upon cooling being directed by said spiral groove through the finned section to precool the fluid flowing to the distribution section, said frusto-conical body being a non-metal through which heat transfer is inhibited to prevent the stem means from being cooled by conduction of the cooled fluid present in said chamber and flowing in said spiral groove.
 2. The head assembly, as recited in claim 1, wherein said frusto-conical head includes: a recess located in said vortex adjacent the spiral groove to hold the orifice of the distribution section in axial alignment with said second blind bore.
 3. The head assembly, as recited in claim 2, wherein said frusto-conical head section further includes: fastener means attached to said distribution section and the finned section to prevent relative movement therebetween. 